Movable contact strip adapted for touch responsive tone control electronic musical instrument

ABSTRACT

A movable contact strip especially adapted for a touch responsive tone control key switch mechanism wherein the tone control depends upon the duration of time during which the movable contact strip is shifted from one stationary contact or break contact to the other stationary contact or make contact. The strip has a portion made more rigid than the remaining portion thereof at least between the point where the strip is actuated by the actuator and the point where the strip makes a contact with the stationary contacts. The existence of said more rigid portion enables the strip to travel well in proportion to the movement of the key, particularly at high velocity, attaining an accurate tone control as desired.

United States Patent 1191 Nagano Apr. 30, 1974 [54] MOVABLE CONTACTSTRIP ADAPIED 3,705,254 12/1972 Amano 84/I.1 FOR TOUCH RESPONSIVE TONE3,708,605 l/l973 Ohno 84/1,] 3,673,303 6/1972 Amano 84/l.0l q fig g fMUSICAL 2,959,693 11/1960 Meyer 84/1.01 x INS R 3,041,568 6/1962BlSSOnelte (it a] ..84/Dig. 7 [75] Inventor: Takehiko Nagano, Hamamatsu,2,497,661 2/1950 Dome 84/l.01 Japan 501,543 7/1893 Singer ..84/l.l l I2,555,040 5/1951 Jordan ..s4/1.01 x 1 3] gne ppon Gakkl Sella Kabushikl3,328,507 6/1967 Peterson ..s4/1.1 x

Kalsha, Hamamatsu-shi, shlzuoka'ken Japan Primary Examiner-Stephen J.Tomsky [22] Filed: July 5, 1972 Assistant Examiner-Stanley J. Witkowskipp No: 269,229 Attorney, Agent, or Fzrm--Flynn & Frishauf ABSTRACT [30]Forelgn Apphcatmn Pnomy Data A movable contact strip especially adaptedfor a touch Sept. 14, l97l Japan 46-84032 res o sive tone control keyswitch mechanism wherein the tone control depends upon the duration [52]US. Cl 84/L1, 84/ 1.27, 84/DIG. 7 of time during which the movableContact strip is [51 Int. Cl. t. Gloh l/00 hift d from one stationaryontact or break contact [58] Fleld of Searc to the other stationarycontact or make contact. The strip has a portion made more rigid thanthe remaining 200/170 R, 1 0 D G- 338/69 portion thereof at leastbetween the point where the strip is actuated by the actuator and thepoint where Refel'flwes Cited the strip makes a contact with thestationary contacts. UNITED STATES PATENTS The existence of said morerigid portion enables the 1,051,675 1/1913 Breed s4/1.1 Strip "ave! inthe movement 1,318,977 10/1919 Dal-Icy n 84] the key, particularly athigh velocity, attaining an ac- 3,634,593 1/1972 Nagano 84/].01 at tonntr l as desired. 3,651,730 3/l972 Adachl 84/].27 X 7 Claims 8 DrawingFigures MOVABLE CONTACT STRIP ADAPTED FOR TOUCH RESPONSIVE TONE CONTROLELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION This inventionrelates to a key switch mechanism for deriving a tone signal from a tonegenerator of a keyboard type electronic musical instrument and moreparticularly to a movable contact strip for use in a key switchmechanism of an electronic musical instrument adapted for a touchresponsive tone control.

A keyboard type electronic musical instrument generally includes keyswitches for deriving tone signals from tone generators upon keydepression. However, these key switches are only used for the deliveryof tone signals from the tone generators, and are not adapted to effecta touch responsive tone control of the level of tone signals produced bythe tone generators exactly in accord with the velocity with which thekeys are depressed.

With the ordinary electronic musical instrument, the

touch responsive tone control is simulated by expression control bymeans of an expression pedal which adjusts the volume of sounds producedby tone signals.

In recent years, there have appeared on the market some types ofelectronic musical instrument capable of touch responsive tone control.One of the touch responsive tone control systems used in these recenttypes of electronic musical instrument is provided with a key switchmechanism consisting of a pair of station ary contacts, that is, a breakand a make contact, and a movable contact strip therebetween which, whenactuated by the key, has its engagement changed from the break contactto the make contact, thereby carrying out the touch responsive tonecontrol, utilizing the fact that the time required for the movablecontact strip to have its engagement changed from the break contact tothe make contact varies with the velocity with which the key isoperated. However, the movable contact strip of the'key switch mechanismof electronic musical instruments just mentioned consists of arelatively soft thin leaf-like member. Such leaf-like member can makeits operating velocity agree with that of a key while it moves slowly,but fails to have the velocity match the rapid movement of the key.Therefore, any of these recent electronic musical instruments fails toeffect full touch responsive tone control exactly in conformity to thekey operating velocity.

It is accordingly the object of this invention to provide a key switchmechanism capable of obtaining full touch responsive tone controlexactly in accord with the key operating velocity.

SUMMARY OF THE INVENTION A key switch mechanism for touch responsivetone control to which this invention is adapted comprises a pair ofstationary contacts, namely, a break and a make contact, and a movablecontact strip fixed at one end and provided at the other end withcontact sections for abutting against the break and make contactsresponsively and, when actuated by the key, so designed as to have itsengagement changed from the break contact to the make contact.

The time required for the movable contact strip to have its engagementchanged from the break contact to the make contact varies exactly inconformity to the velocity with which the key is depressed.

In order to provide the corresponding relationship of the timeabove-mentioned with the key velocity (the time varies inversely withthe key velocity), according to the present invention the actuatingportion of the movable contact strip is intermediate the ends of thestrip, and, that portion of the movable contact strip which is definedbetween the actuating point at which the .movable contact strip isactuated by the key and the aforementioned contact sections is providedwith means for rendering the portion more rigid than the remainingportion thereof.

According to an embodiment of this invention, the aforesaid specifiedportion of the movable contact strip has a rib formed along thelengthwise central line thereof.

According to another embodiment of the invention, the specified portionof the movable contact strip has elongate protrusions disposed alongboth lengthwise edges thereof.

According to still another embodiment, the specified portion of themovable contact strip is made thicker than the remaining portionthereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a touchresponsive tone control system for which the present invention isadapted;

FIG. 2 represents a relationship of the operating velocity of a key andthat of a movable contact strip;

FIG. 3 is a schematic side view, partly in section, showing the relativepositions of a key and a key switch for touch responsive tone control;

FIG. 4A is a top view of a movable contact strip according to anembodiment of the present invention;

FIG. 4B is a sectional view on line 4B-4B of FIG. 4A;

FIG. 5A is a top view of a movable contact strip according to anotherembodiment of the present invention;

FIG. 5B is a sectional view on line 58-58 of FIG. 5A; and

FIG. 6 is a longitudinal sectional view of a movable contact stripaccording to still another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 thereference numeral 1 represents a key actuated switch consisting of amovable contact strip 2, a stationary (break) contact 3 and anotherstationary (make) contact 4. The movable contact strip 2 normally abutsagainst the break contact 3 to constitute a path for charging acapacitor 5 from a DC source or battery 6. A resistor 7 is connectedparallel with the capacitor 5 to constitute a discharge path thereof.The make contact 4 is connected to a diode 8 disposed in the forwarddirection with respect to the polarity of the battery 6 and to acapacitor 9 which stores the voltage of the capacitor 5 when the movablecontact strip 2 is switched or shifted from the break contact 3 to themake contact 4. The voltage stored in the capacitor 9 is supplied to akeyer 10 which is already impressed with a tone signal from a tonegenerator 11. The keyer 10 may consist of, for example, a variableresistor comprising a field effect transistor.

The tone signal from the tone generator 1 1 is drawn off through theconduction path defined between the source and drain of the transistorand conducted to a utilization circuit including tone coloring filtersand amplifiers. The voltage stored in the capacitor 9 is supplied to thegate of the aforesaid transistor to control conductivity across thesource and drain thereof.

There will now be described by reference to FIG. 1 the operation of atouch responsive tone control system for which the present invention isadapted. The time required for the movable contact strip 2 to have itsengagement changed from the break contact 3 to make contact 4 isexpected to vary in accordance with the velocity with which the key isoperated. Accordingly, the amount of voltage discharged from thecapacitor 5 through the resistor 7 also varies in accordance with thekey operating velocity. It will be apparent, therefore, that the levelof the voltage stored in the capacitor 9 when the movable contact strip2 abuts on the make contact 4 also varies in accordance with the keyoperating velocity. Since conductivity across the conduction path of thetransistor is controlled by the voltage of the capacitor 9 accuratelymatching the key operating velocity, there can be drawn a tone signalfrom the keyer 10 at a level varying in accordance with the keyoperating velocity.

FIG. 2 shows the relationship of the key operating velocity and thevelocity with which the movable contact strip changes its position. Withthe prior art movable contact strip, the operating velocity of themovable contact strip indicates, as illustrated in a solid line, somedelay from the key operating velocity when it considerably increases,though the velocity of the movable contact strip presents a linearagreement with the key operating velocity while it falls within acertain range, thus failing to provide good touch responsive tonecontrol as intended. The broken line of FIG. 2 shows the ideal operatingvelocity of a movable contact strip substantially matching or inproportion to the movement of a key, for which this invention isprimarily intended.

FIG. 3 is a schematic sectional view showing the relative positions ofthe key and key switches. Below a keyboard frame 20 supporting a largenumber of keys 21 (only one indicated) are disposed key switches lassociated with the respective keys 21. The movable contact strip 2 ofthe key switch 1 is fixed at one end to an insulation member 22 andnormally abuts at the other end against the break contact 3. The makecontact 4 is disposed below the break contact 3. To the underside of thesubstantially central part of the key 21 is attached an actuator 23,which extends through the frame 20 down to the movable contact strip 2.When the key 21 is depressed, the actuator 23 causes the movable contactstrip 2 to have its engagement changed, as indicated in a broken line,from the break contact 3 to the make contact 4.

In this case, the operating velocity of the prior art movable leaf-likecontact strip fails, as previously described, exactly to follow themovement of the key for the reason given below. The outermost or freeend of part by the key, it presents flexure or sagging between the pointat which it is depressed by the actuator and the free end. Since,however, the free end alone tends to be brought back to its originalposition due to its inertia, the movement of the free end fails exactlyto accord with that of the key, especially at higher speed. Thisinvention eliminates the above-mentioned drawback by imparting greaterrigidity to that portion of a movable contact strip which is definedbetween its free end and the point at which it is depressed by the keyactuator than the other portion of the contact strip.

FIGS. 4A and 4B jointly illustrate a movable contact strip according toan embodiment of this invention. This movable contact strip has a rib 27formed along a lengthwise central line between its free end 26 and thepoint 25 at which it is depressed by the actuator 23 upon key depressionso as to render the ribbed portion more rigid than the other portion ofthe contact strip. The reason why there is not formed any rib in thatportion of the contact strip which is defined between the aforesaidpoint 25 and fixed end 28 is that the latter portion should be fullyflexible. Both sides of the free end 26 are provided with contact pieces29 which are made to abut against the break and make contacts 3 and 4respectively.

The movable contact strip may be prepared from nickel silver. When themovable contact strip was made of a sheet of nickel silver, thedimension of the strip was selected such that: the distance between theactuated point 25 and the center of the contact piece 29 was 15 mm; thedistance between the actuated point 25 and the end of the strip 2 fixedto the insulation member 22 was 25 mm; the thickness and width of thestrip were respectively 0.14 mm and 4.0 mm; and the rib 27 extended fromthe actuated point 25 toward the free end 26 was 1 mm wide, 0.5 mm high,and 10.5 mm long, whereby there were obtained good results.

According to this invention, the contact piece 29 at the free end 26 isprepared by depositing a layer gold, silver or alloys thereof to providegood electrical contact between the contact piece 29 and the break andmake contacts 3 and 4.

FIGS. 5A and 5B collectively show a movable contact strip according toanother embodiment of this invention. This contact strip has elongateprotrusions 30 extending perpendicularly to the plain of the strip,instead of a rib 27 of FIGS. 4A and 43, formed along both lengthwiseedges of a corresponding portion to the ribbed portion of FIGS. 4A and4B which similarly extend from the actuated point 25 toward the free end26, thereby rendering the portion more rigid than the remaining portionof the contact strip.

FIG. 6 indicates a movable contact strip according to still anotherembodiment of this invention. Most of the portion of the contact stripwhich is defined between the actuated point 25 and the free end 26 isformed into a thicker section 31 than the remaining portion of themovable contact strip so as to be rendered more rigid. The thickersection 31 may be formed fully transversely across the movable contactstrip in substantially the same length as the rib 27 of FIGS. 4A and 48.

What is claimed is:

1. An electronic musical instrument for deriving a tone signal from atone generator upon key depression with the tone signal level beingvaried in accordance with the velocity of operation of a key by theoperator, comprising:

a tone generator;

means for controlling the-tone signal level of the tone signal generatedby the tone generator;

contact to said make contact when actuated by v the key at saidactuating portion; and

stiffening means on said'movable contact strip between said actuatingportion and said contact section for rendering a portion of said movablecontact strip which is located at least between said contact sectionsand said actuating portion more rigid than the remaining portion thereofand for causing the velocity of movement of said contact sections to bea function of the velocity of movement of said actuating portion.

2. Apparatus according to claim 1 wherein said stiffening meanscomprises at least one rib formed on the surface of the movable contactstrip along its lengthwise direction.

3. Apparatus according to claim 1 wherein said stiffening meanscomprises protrusions formed along both lengthwise edges of said movablecontact strip.

4. Apparatus according to claim 1 wherein said stiffening meanscomprises a portion of said movable contact strip made thicker than theremaining portion thereof.

5. Apparatus according to claim 4 wherein said thicker portion extendssubstantially transversely across said movable contact strip.

' 6. Apparatus according to claim 1 wherein said controlling means isresponsive to the time for said movable contact strip to be switchedfrom said break contact to said make contact.

7. Apparatus according to claim 6 wherein the tone signal level iscontrolled to be a function of said time.

1. An electronic musical instrument for deriving a tone signal from atone generator upon key depression with the tone signal level beingvaried in accordance with the velocity of operation of a key by theoperator, comprising: a tone generator; means for controlling the tonesignal level of the tone signal generated by the tone generator; a keyswitch mechanism coupled to said controlling means for causing the tonesignal level to be a function of the velocity of operation of the key,the key switch mechanism including: a key; a pair of break and makecontacts; a movable contact strip fixed at one end and provided at theother end with contact sections for abutting against said break and makecontacts, said movable contact strip having an actuating portionintermediate the ends thereof coupled to the key and being switched fromsaid break contact to said make contact when actuated by the key at saidactuating portion; and stiffening means on said movable contact stripbetween said actuating portion and said contact section for rendering aportion of said movable contact strip which is located at least betweensaid contact sections and said actuating portion more rigid than theremaining portion thereof and for causing the velocity of movement ofsaid contact sections to be a function of the velocity of movement ofsaid actuating portion.
 2. Apparatus according to claim 1 wherein saidstiffening Means comprises at least one rib formed on the surface of themovable contact strip along its lengthwise direction.
 3. Apparatusaccording to claim 1 wherein said stiffening means comprises protrusionsformed along both lengthwise edges of said movable contact strip. 4.Apparatus according to claim 1 wherein said stiffening means comprises aportion of said movable contact strip made thicker than the remainingportion thereof.
 5. Apparatus according to claim 4 wherein said thickerportion extends substantially transversely across said movable contactstrip.
 6. Apparatus according to claim 1 wherein said controlling meansis responsive to the time for said movable contact strip to be switchedfrom said break contact to said make contact.
 7. Apparatus according toclaim 6 wherein the tone signal level is controlled to be a function ofsaid time.